Torus is an impressive 3D Tetris game powered by HTML5
You rotate the ring itself with the arrow keys, while a Tetris-like piece slowly (excruciatingly slowly, in fact) descends from the top. As soon as you make a solid line, it disappears.
Not all pieces are Tetris-like; some of them wouldn't really work with a regular Tetris game but are a good fit for Torus' 3D format.
Torus is ideal for playing at the office, because it has absolutely no soundtrack. The game is dead-quiet. It's also very very slow (slow enough for me to mention it twice in one post) so you can safely look away for a moment and then keep playing. Also, as soon as the game loses focus, it automatically pauses.
Bottom line: It's an impressive demo of the power of HTML5; if it were a bit faster, it would have some serious addictive potential.